Compression and microstructure of fibre plain woven cloths in the processing of polymer composites

The compression of a typical fibre plain woven cloth was studied experimentally by performing a series of mechanical tests on dry and resin impregnated cloths and from microstructural studies of specimens cured under compression. The experiments included investigations of the effects of applied pressure, speed of compression and cloth orientation on the fibre volume fraction, V-f, of the compressed assembly. It was found that the compression of dry cloths followed a power law relationship between pressure and V-f where the power law index was determined to be approximately equal to 10 for assemblies of 5, 10 and 20 dry cloths. The microstructural studies provided data for the distance between plies, the amplitude and the wavelength of the yam waveform and the area and geometrical parameters of the yam cross-section at different compression pressures. It was concluded that the compression of resin impregnated woven cloths could be considered as a combination of three modes of deformation: (1) nesting of cloths; (2) deformation of the yam waveform, and (3) deformation of the yam cross-section. (C) 1998 Elsevier Science Limited. All rights reserved.